Adolph a



Reissued Mar. 4,

UNITED STA ADOLPH A. THOMAS,

TES PATENT OFFICE- F NEW YORK, N'. '.Y.

ELECTROMAGNETIC TBANSLATING DEVICE Original No. 1,630,640, dated May 31, 1927, Serial. No. 78,279, led December 30,1925.' Application for reissue led April 6, 1929.V Serial 110,353,233.

My invention relates to sound-reproducing devices, and Aits object is to provide new and improved sound reproducer particularly adapted for use in phonographsl and similar apparatus.

0 erate with electromagnetic mechanism to generate current impulses in accordance with the vibrations of the arm. When my invention isA embodied as a phonograph. reproL ducer, the vibratoryl arm is actuatedat one end by a record-needle, and the vibrations of the needle are transmitted to the magnetic member in amplified ratio. In the broader aspect of my invention, the vibratory arm may be mechanically actuated byv any other acoustic means for electrically reproducing sound. A t

' In a preferred embodiment vof my inven` tion, the reproducing arm is mounted on a spring, which performs the-double function of supporting the arm and resiliently holdmg it in normal predetermined' position. This spring, in its simplest form, is a fiat blade held fast at itsends, and the arm is securedto the middle of the spring. The mountingl of the spring is such that it is capable of a twisting or torsional movement to permit ready vibration of the arm laterally from its normal position in either direction. At the same time, the spring fully takes up the longitudinal thrust or strain exerted on the arm during its operation'. This resilient mounting of the vibratory arm produces a construction of great simplicity', as it obvatesvthe necessity of separate restoring or centrahzing springs.

Une of the marked advantages of -my electric reproducer results from the extreme lightness and correspondingly low inertia ofthe vibratory unit, whereby the same responds freely and correctly to the mechanical actuations of the vibratory arms. vFurthermore, the electromagnetic mechanism may be so constructed that the magnetic member on the arm exerts. no appreciable magnetic drag or lag on the arm, thereby enhancing the'` degree of faithfulness of reproduction.

.The instrument of my invention is of special advantageV in ,reproducing from Y phonograph records having several hundred lines' to the inch and playing for half an hour or more. In these records, the walls of adjacent grooves are necessarily frail, and the needle vibrations' are of eXtreme delicacy. With such finely grooved records, an ordinarymechanical reproducer having a stiff diaphragm of essentiallyhigh inertia is out of the question. The same objection applies, atleast to' alarge extent, to a microphonic reproducerin which a-diaphragm operates against packed resistance granules. Now, in

the reproducer of my invention, there" is'no diaphragm, the vibratory unit is very lightv and of low inertia, :so that it responds .in-

stantly and faithfully to the needle vibrations. Since these vibrations are transmitted to the magnetic member in amplified ratio, the slightestmovements of theineedle cause current impulses to be generated by this member. A

In the accompanying drawings I have illustrated several embodiments of my invention, which I shall now describe in detail, so that those skilled in the art may understand the same. I wantto make it-clear, however, that these constructions are merely practical examples and not limitations of my invention. 'In these drawings,

Fig. 1 shows an interior faceview, partly in section, of a phonograph reproducer constructed in accordance with my invention;

Fig. 2 represents a cross-section on the broken line 2 2 of Fig. 1;

, Fig. 3 is a top plan' view in section on t-he broken line 3-3 of Fig. 1;

Fig. 4 is a side view of a modified form of spring mounting for the needle arm;

5 is a cross-section' approximately on th'e broken line 5-5 of Fig. 4;

Fig. 6 is a cross-section on line 6-6 of Fig. 5;

Fig. 7 illustrates a side View, partly in section, of a modified form of reproduce; embodying my invention; and

Fig. 8 represents a plan view of the construction shown in Fig. 7.

Before going into a detailed description of these drawings, let me explainvthat the various parts have been purposely exaggerated in proportion and spacing, so as to make the drawings as clear as possible. The actual device would be considerably smaller than the illustrations. f

I shall first describe the construction shown in Figs. 1, 2 and 3. The various parts of the instrumentv are mounted. in a casing indicated as a whole by C, comprising a back plate 1, a body section 2, and a front plate or cover 3. These parts are preferably made separate and removably secured together by screws 4, or other fastening means. The casing parts may `be constructed of light,

non-magnetic'material, suehas aluminum,

or an aluminum alloy, or they may be shaped out ofbakelite or other suitable insulating composition. In the latter instance,

the parts 1 and 2 could be molded as a. single cup-shaped piece. The back plate 1 of the casing is provided with a hub 5' for mount- "ing 'the instrument as a whole on a suitable arm 6. Since the particular embodiment `I am` describing is shown in the form of a phonograph reproducer, the arm 6 is supposed to be properly mounted to allow th reproducer to travel over a record. i

Within the casing C is mounted a magnet M preferably of the permanent type. The magnet may be solid or composed of thin laminations. In the present instance, the

vmagnet Mis fixed to the back plate 1 by means of screws 7 but it may be supported in the casing in any other practical way. As seen from Fig. 1, the magnet is U-shaped and follows closely the outlines of the rectangular body section 2 of the casing, thus providing a magnetic path of' maximumv length in a small space.' The legs of the magnet are bent forwardly, as indicated at 8, and then turned upwardly to form the polar ends 9.' To eachV polar end is secured a U-shaped pole piece 10, as best shown in Fig. 3. These polar pieces are made preferably of soft iron, solid or laminated, and are firmly secured. to the magnet by screws 11'01" otherwise. Each pole piece 10 has a pair of limbs 12 and 13, whichextend toward each other to form a pair of transversely aligned airgaps 14 and 15. On one orboth polar limbs 12 is mounted a coil or coils 16.

. In the present instance, the coil 16 consists of two windings electrically connected, as

` indicated at 17, so` as to formin effect a single coil. If the 'coil or coils 16 project beyond the width of the body section 2 of 'the casing, the front plate or cover.A 3 is l formed with a bulge 18 to `.accommodate the coils, but the magnetic structure with its pole pleces and coils may be so designed that a -comparatwe shallow casing. will house all the parts. It` will be noticed that the.,

magnet -M may be fully equipped with the pole pieces 10 and the coil or coils 16 be fore being inserted into the casing.

lThe central body section 2 of the casing is provided at its lower end with a pair of transversely aligned lugs 19, having each a slot 20 for receiving the 'ends of a spring blade 21, which is fixed in position by screws 22 or otherwise. At or near the center of the spring blade 21 is. fixed a needle arm 23 in any practical way, as by means of a rivet By looking atFig. 2, it will be seenthatv when` the needle of the reproducer rests on a record in playing position, the longitudinal thrust against the arm` 23 is in the plane of the'flat spring blade 21, and is therefore readily taken' up by the spring. When the needle vibrates laterally (as viewed in Fig. 2"), the leaf spring 21 is twisted sideways at the center and the needle arm 23 is allowed to vibrate back and forth in the casing. In other words, the leaf spring 21 not only supports the needle arm against longitudinal movement, but also.v constitutes a solid pivot bearing for the needle arm. Furthermore the spring support 21 normally holds the arm 23 in a neutral position, so that the arm is readilyjy vibrated in opposite directions from its normal position. The part 21, therefore, performs a triple function and thus simplifiesthe construction.

On Ithe free or inner end ofneedle arm 23 is mounted an armature 28, which is a soft liron piece of the proper. dimensions, dependless width. than these airgaps.` In Figs. 2

and 3, I have shown the armature 28 slightly overlapping the polarlimbs 12 and 13 at its ends. The torsional spring support 21 normally holds the armature 28 in a practically neutral position midway between the airgaps 14 andv 15. That is to say, the-armature is normally balanced by the opposingmagnetic pulls at its ends, lso that the arm 23 is normally free from any strain or pull in .the plane of its vibrations.v stood from Fig. 3. y

` It will be clear that as the needle arm 23 'vibrates back and forth, the magnetic flux passing through the coil or coils l16 is correspondingly varied. lThat is to say, when the armature moves ytoward the airgap 14,

This is easily under-` i the greater portion of the Vfield flux passes through the polar limbs 12 and the coil or coils 1,6. kWhen the armature 26 moves into the airgap 15, the ,greater "part of the iield flux is shunted through the polar limbs 13, whereby the iux passing through the windings 16 is decreased. The amount of variation of the number of lines of force passing y through the coil or coils16 depends upon the l ture.

amplitude of vibration of the armature 28,

and the rate of magnetic variation depends upon the frequency of vibration of the armaincreased variation has an amplifying effect on the coil 16. Furthermore, since the armature 28 is at a considerablyV greater distance from the spring support21 than is the point of the needle 27, the vibrations of the needle are transmitted tothe armature in amplified ratio, so that the minutest vibrations of the needle vproduce movements of the armature sutlicient to generate current impulses inthe coil or coilsmounted on the magnet. In order to maintain the vibrating armature 28 in complete alignment with the polar'limbs 12 and 13, the upper and lower surfaces of'the polar limbs and armature may becurved on the arc of a circle struck up fromL the axial center ott the spring plate 21. This curvature of the polar limbs and armature is indicated in Fig. 2. This detail, however, is not necessary, since the armature vibrations are comparatively small;

The coil or coils 16 are connected in a circuit leading to suitable amplifying apparatus, which need not be shown or described, since it forms no part of my invention and is furthermore well understood by those skilled in the art.l In Figs. 1 and 2, I have shown a pair otinsulatedv binding posts 29, to which the ends 16 of the windings 16 are connected. It the supporting arm 6 is tubular, the circuit connections 30 leading lfrom the binding posts 29 may be concealed within this hollow arm, .thereby imparting a neater appearance to the phonograph as a whole.

In F'gs. 4, 5 and 6, I have shown a modilied form of spring support for the vibratory needle arm. In this construction, the spring blade 21 is given an initial torsional tension by slightly twisting the ends in opposite directions, as indicated at 31 and 32. This places the central section of the spring in a neutral or balanced condition, and to this balanced section of the spring is secured a needle arm 33 of proper shape and dimen- The variation of the magnetic lux.

sions. A convenient way of attaching the needle arm to the spring is by providing the arm with a lrecess 34 in which the spring 21' is tightly tted. A plate 35 is then laced over the spring, and a screw or other astening member 36 rigidly secures the parts together. The ends 31 and 3 2 of spring 21 may be mounted in any suitable way to give them the desired degree of initial torsional tension.4 B Way of example, I have shown a pair of. ugs 37 and 38 projecting from the lower end of the casing, similar to the. lugs 19 of Figs. 1 and 2. Thelugs 37 and 38, are provided each with a slot 39 of a configuration as shown in Fig. 4. That is to say, each slot 39 has a lower narrow portion 40 and an enlarged portion formed by -a slanting side 41.A Inthe lugsf 37 and 38 are mounted set-screws 42 and 43 arranged to project into the enlarged portions ot' the slot-s 39. They ends of spring 21 fit tight into the narrow portions 40 of these slots. If desired, small end plates 44'may` beV secured to the lugs. 37 and 38 across the narrow portions 40 of the slots, so as to positively lock the spring 21 against accidental movement in a longitudinal direction: The set-screws 42 and 43 bear against the ends vof the spring at or near the upper edge thereof, whereby these ends may be liexed laterally in the enlarged portions of the slots 39. This will be, clearly understood from Fig. 4'. The slots 39 are arranged oppositely in the lugs 37 and 38; in other Words', the

slanting sides 41 of the slots are positioned reversely with respect to the spring ends. By adjusting the screws 42 and 43, the initial lateral twist yor turn given the spring ends may be regulated to the proper degree, so that vthe needle arm 33 is normally held balanced in predeterminedposition. The opposing torsional strains at the ends of spring21' permit ready vibrations of the needle arm laterally of the spring, as previously explained in reference to sprmg arm- 23 of Figs. 1 and-2. The spring support of Figs. 4,-5 and 6 may be considered to be substituted in Figs. 1 and 2, but in the broader aspect of my invention, any practical' electromagnetic reproducing mechanism may be associated with my novel construction ot spring support for the needle arm.

In the modification of Figs. 7 .and 8, there y is a permanent U-shaped magnet M secured to the back wall of, a casing C of proper construction and design. To the ends of magnet M are secured forwardly projecting pole pieces 45, usually made of soft iron, and one or both of these pole pieces carry a winding 46. If two windings 46 are used, as shown in Fig. 8, they are connected in series so as to constitute a'single coil. When I speak ofthe coil 46, therefore, I mean either A one or more windings. The pole pieces 45 are separated'by an airgap 47, in .which 1 to the eficiencyof the instrument. Some of vibrates an armature 48 attached to the inner end of a needle arm 49. The armature 48 is a piece of soft iron of the proper dimensions, so as to lit closely in the airgap 47 Without touching the pole pieces. The armature 48 is normally held in a position in which it projectspart way into the airgap 47. Consequently, when the needle arm 49 vibrates iu onedirection the armature 48y moves farther into the airgap to increase the magnetic flux through the coil 46. During the reverse movement of the needle arm, the armature moves fuither out of the airgap and thereby decreases the magnetic iux through the winding. The needle arm 49 is mounted in any practical wayon the casing C'. In the present instance, this arm is pivoted at 50 by a bearing at the lower side `of the casing. It will be observed that the vibrations of the needle attached to arm 49' are transmitted in amplified ratio to the armature Suitable spring means, such as a pair of leaf springs 51, hold the needle arm in normal position. In place of the pivot bearing 50 and the centering springs 51, the combined supporting and centralizing spring 21er 21 may be used.`

Attention is called to the fact that the armatures 28 and 48 are so arranged in the magnetic airgaps that any tendency of the pole pieces to attract the armature laterally is at right angles to the plane of vibration of the `needle arm. Consequently, any lateral magnetic drag that may develop by reason of theariiiature being slightly closer to one pole piece than to the other, exerts no drag or load (certainly to no disturbing extent) on the vibrations of the needle arm. Furthermore, any magnetic side pull on the armature (and therefore on the needle arm) is fully taken up by the'mounting of the arm, particularly if the spring support 21 or 21 is used.

Another practical advantagej of my con#` struction lies in the fact that the luX variations produced byv the vibratory armature take place in the soft iron pole pieces and not in the steel body of the magnet. This increases the. sensitiveness of the instrument, because soft iron has greater magnetic permeability than steel and offers little resistance to changes in magnetic iux.

It should be noted that the operative air` 'gaps 14 and 15 of the magnet structure are narrower than the distance between the polar projections 12 and 13 of Leach pole piece.'l

These narrow airgaps permit the passage of the normal `field flux from one pair of polar projections 'to the other with a minimum amount of magnetic leakage, thereby adding the iield flux'will, of course, pass through the extreme ends of the armature structure 28, but the flux never,passes lengthwise through vwhich my the armature to saturate the same. The armature therefore responds instantly and accuiately to electric impulses in the coils 16 when the instrument is used as a receiver. As previously stated, the vibratory unit is of low inertia, which means that the armature is made comparatively light. To avoid any possibility of misinterpretation or confusion as to what I mean by the width of the airgaps 14 and 15, I wish to make it clear that I refer to the distance between the opposed polar faces which form the airgaps, and I do not refer to the length or width of the polar projections, which may have such dimensions as may be found most suitable in any particular design of instrument. y 1 y It will be seen from the foregoing descriprtion that I have provided an electric sound reproducer of exceedingly simple construction and capable of faithfully reproducing the most delicate vibrations of a phonograph Aneedle or performing any other useful function.` Of course, it' is -assumed that the parts are properly designed, proportioned and assembled. No rule can be' laid down as to the precise dimensions of the parts,

.for these are matters of experiment well Within the skill of the artisan trained in this particular line of science.

In the broader aspect of my invention, the

vibratory arm or lever which carries thearmature maybe mechanically actuatedV at lts outer end by other means than'a phonograph needle. It is possible, for example,

to connect a transmitting diaphragm with or to the outer end of the needle arm, and if this diaphragm is actuated by sound Waves motion. In this way, my new instrument may be used as a telephone transmitter capable of use in broadcasting and similar field of utility. Also, it is manifest that electric impulses passing through the coils 1G or 46 causevibration of the armature structure to operate any suitable member or mechanism.

Although I have shown and` described certain specific constructionsit'is apparent that the various features .of my invention graph in its broadest possible sense of .,recorded sound. The particular type or name of sound-reproducing .machine in invention is embodied, is immaterial. Y

What I claim as my invention'is; 1. In an electric phonograph reproducer free from an acoustic diaphragm, a vibrallO tory lever adapted to be actuated by the. 1. u

vibrations of'a .record needle, said lever comprising a short arm and al lng arm, a permanent magnet having poleV pieces, a .magnetic member mounted on the free end of said long arm inoperative relation to said pole pieces, whereby theneedle vibra? tions are transmitd in amplified ratio tol said member,non-acoustic resilient means for holding said needle arm and magnetic member in predetermined normal position, and a current' generating coil vcontrolledby the movement of said member. I

2. An electric phonograph reproducer comprising a rcasing,fa substantially U- shaped magnetmounted in said .casing .with its legs extending upwardly so lthat the pole pieces terminate near the upperend of the casing, a needle arm pivotedtto the lower end of said casing, the pivot pointof said needle arm, being arranged that the needle vibrations are transmitted tothe inner end of thev armin amplified ratio, an armature mounted on the inner end of said 4needle arm to vary the magnetic flux'through said pole pieces, and a coil on oneof said pole pieces. 1

3. ln an electromagnetic translating. device a magnet provided with two pairs ofoppositely arranged pole pieces forminga pairv of aligned airgaps, said pole pieces and airgaps constituting two parallel paths for the magnetic'fluX,-a pivoted lever adapted to -beactuated at-one end,'an armature mountedv on the yother end of said lever and arranged to i reciprocate between said airgaps ,'so that one end of said armature moves toward oneof" the airgaps while the other end moves away from the other airgap, whereby/.the magnetic'flux is increased through one of said parallel. paths and simultaneously decreased through the other path, vand a' Goilfeifected by Iiux variations through said paths. l

4. lin an electric phonograph-reproducer, a casing, a magnet secured to a wall of said casing, said magnet consisting of a subst-an.-

tially U-shaped body lying flat against said wall and having a pair of polar projections extending away from said wall, said magnet being so mounted that the legsthere'of extend upwardly so that the polar projections are near the upper part of said casing, said pole projections being arranged to provide an airgap, a coil on at least one o-f said polar pro- ]ections, a needle arm pivoted to the lower part of said casing and extending upwardly toward said polar projections, an armaturev mounted on the innerend of said arm to vibrate in said airgap in amplified relation to the needle vibrations, and non-acoustic" resilient means for holding said needle arm and armature in predetermined normal position.

5'. An electric phonograph reproducer comprising a' casing, a needle arm pivoted to the lower portion of said casing s o as to vibrate transversely thereof, an armature mounted '0a the free inner end ofsaid arm which atri Inmates near the upper portion of said casing, so that the needle vibrationsare transmitted in ampliiied ratio to said armature, the vibrationsof said armature being in a plane at rightan'gles to the plane of said casing, and

electromagnetic mechanism. mounted within saidc'asing for generating currents in a'ccordance with the amplified vibrations of said armature. y

6. An electric phonograph reproducer comprising-a shallow casing having substantially parallel front and rear walls, a magnet mounted in said casing against one of said walls and having an airgap near the upper portion of said casing,a needle arm pivoted to the lower portion of said casing .so as to vibrate transversely thereof between said walls,

a magnetic membermounted on the inner end of said arm to vary the linx across said airgap, 'and a current-generating coil controlled by the vibrations of saidv magnetic member.

7. In an electric phonograph reproducer,

[a casing providedv at Aits lower end with a Vpivoted needle-holder, a vibratory' arm. arranged within said casing and connected at its lower end with.saidtneedle-holder, a magnet so` mounted in said casing that the magnetic airgap is near the uper end of the casing diametrically opposite said needle-holder, a

coil associated with said magnet, and a magnetic member mounted on the free end of said arm to vibrate in operative relation'to said airgap,A the length of said arm being such that the 'needle vibrations are transmitted to said magnetic member in ampliied ratio to generate variable currents in the circuit of said coil.

8. An electric phonograph reproducer cornprising a` shallow casing having substantially Aparallel front and reark walls, a magnet mounted in said casing against one of said `walls and having polar faces arranged to form a pair of aligned airgaps extendingv l transversely of said casing in a direction at right angles to the walls thereof, a needle arm p ivoted to saidcasing so as to vibrate in a plane perpendicular to said walls, an armature connected to the free end of said needle arm and arranged to vibrate between said air ra` s transversel of the casinff in a ath c y n p substantially parallel with said polar faces, and a coil controlled by said armature.A

9, In an electromagnetic translating device, a magnet. having a pair of U-shaped pole pieces arranged to provide a pair of aligned airga-ps, a coil surrounding the limb of one of said pole pieces, a pivotedl lever comprising a short arm and a long arm, acoustic means for mechanically vibrating said short arm,

:andan armature attached to the v'free end o-f said long arm to vibratebetween' said airgaps in ampliiedrelation to the short arm.

10. An electric. phonograph reproducer movements of the end of the needle arm to vibrate' between said airgaps and thereby vary the magnetic fluir through said coil, the needle vibrations Y of said arm being transmitted in amplified ratio to said armature, and means for nor- -mally holding said armature ,substantially midway of said airgaps.

11. In an electromagnetic translating device, a magnet having bifurcated pole pieces arranged to provide at least two aligned operative airgaps formed between .pairs of polar faces of opposite polarity, the distance between each pair ofsaid` opposite polar faces being less than the distance betweenthe bifurcations'of said polepieces to provide rela- Vtively narrow airgaps across which the flux of said magnet passes in parallel paths, an Y armature structure arranged to vibrate between saidV airgaps in a direction substantially parallel with said-polar faces and' at right angles to the passage of flux across said airgaps, so that the vibrations of said armature structure increase lthe magnetic ield'ux through one of said parallel paths and simultaneously decrease the ux through the-other path, resilient means for guiding said arma- Iture-,structure across the said opposing polar faces with constant clearance, at least one coil mounted on said bifurcated pole pieces,

' with aligned airgaps, a vibratory needle arm and an operative member connected to said armature structure. A .12. In an electricpho'nograph reproducer, L a -inagnet having pole pieces arranged to` provide a pair of parallel magnetic paths carrying an armature arranged to vibrate between said airgaps in a direction at right angles to the passage of flux across said airgaps, so that Athe vibrations of said armature increase the magnetic eld Hux through one lof said parallel paths and simultaneously decrease the flux through the other path, and

a coil mounted on one of said pole pieces.

13. In .an electromagnetic translating delvice, a magnet having a pair 0f U-shaped `pole pieces arranged 'to provide al pairof.

aligned airgaps, a coil lsurrcundin,f the limb of one of lsaid pole pieces, a vibratry lever comprising a short arm and along arm, a torv. sional resilient spring blade .for 'pivotally "supporting said lever, acoustic means for mechanically vibrating said short arml andv an `armature attached to the freeend of said i long arm to vibrate between said airga s in amplified relation'to the movements o the short arm, saidsupporting spring lnormally holding said amature substantially midway of said airgaps. 4

14.` In a phonograph reproducer, a single l'at Spring blade supported solely at its ends and laterally twistable between .said ends,

means for placing said spring blade under normal tension, and a needle arm secured to and supported by said blade which also forms a solid pivot bearing for said'arm.

15. In a phonograph reproducer, a single ilat torsional spring blade supported solely at its ends so as to lievin aplane practicallyat right angles to the lane of a playing record', aneedle arm lattached to and supported by said spring,- and means .for placing said sprin `under initial torsionald strain by later# ally 'splacing the ends thereofin opposite mal predetermined position.

16.A A honograph reproducer having a i ss directions to hold said arm resiliently in norf single flat spring blade supported solely at i its ends and capable oflateral 'twisting move ments in opposite directions at its central portion, a needle' arm attached to said blade at or nearthe center. thereof, so that said blade not only supports said arm against longitudinal movement but also constitutes the sole pivot bearing for the lateral vibrations of said arm, and a reproducing element operated by said arm. v

17. In a phonograph reproducer, a single flat torsional spring blade supported solely at its endsso as to lie ina planeY practially at right angles to the plane of a playing record, and a needle arm attached to said spring and supported solely thereby, said spring blade also constituting the sole bearing for the pivotal movements of said arm. 4 A

18.- In a phonograph reproducer, a single ,dat twistable spring blade supported solely atv its ends in bearings, means for adjusting said beaijings late rally of said spring blade in opposite directions to place the same under initial torsional strain, and a needle arm se cured to the center of said blade and supported thereby against longitudinal movement, said blade also orminga pivotal bearing for said arm. i

' 19.V An electromagnetic translating device comprising a permanent magnet structure provided with polar projections havingv end faces 'of opposite polarity arranged Vto provide at least a pair of aligned operative airgaps through which the normal field flux passes parallel paths, the width of said airgaps Vbeing lessl than [the distance between polar projections of like polarity, a vibratory member, an armature structure connected to said member and arranged lto reciprocate between said airgaps Vso that the :magneticV reluctance across one airgap is. decreased and the magnetic reluctance across the other airture structure being mounted to vibrate in a pathsubstantially parallel with said polar faces, and a coil operatively associated with .said magnet to cause vibration of said armature structure and member or to'generate current, impulses in accordance with the vibrations of said structure and member.

20. A phonograph reproducer comprising a casing mountedto travel over a record, a single flat spring blade iixed at its ends to said casing. and arranged in a planesubstan-y of said arm is practically in or along the plane of said blade, which thus acts as a firm 21. In a phonograph reproducer, a single flat spring blade supported solely at its ends s and laterally twistable between ysaid ends,

screw-threads.

to the center of said blade.

means for supporting the ends of said blade in reversely inclined positions, whereby said blade is normally tensioned, said supporting means including adjustable screws-whichact like positive stops to counter-act the pressure or thrust of the tensioned spring blade in ia direction substantially at rightangles to the screw-threads, and a stylus holder connected f 22. In an electromagnetic reproducer, a single flat spring blade laterally twistable andsupported solely at its ends `for vibratory movement, an armature connected to said spring blade," a magnet system operatively vassociated with said armature, andaneans for adjusting said spring blade to vary, the nor mal position of said armature, said adjusting means including adjustable screws which act like positive stops to counter-act the pressure or thrust of the tensioned spring blade in a direction substantially at rightangles to the 23. In an electromagnetic reproducer, a support comprising a pair of reversely inclined members, a resilient strip supported in tensioned condition between said members for vibratorymovement, an armature carried by said strip, and amagnetic system operatively associated withv said armature, said support including adjustable screws to adjust the normal position of said armature.

24. In an electric translating device, a pair 'of supports having opgpositely inclined pormovements' of said member into :electric impulses.

lan electromagnetic translating de-l vice, amagnet system havingan armature,

a resilient vibratory strip supporting said armature, and a pair of spaced supports'for the endsof said strip, said supports having oppositely inclined port-ions over which the s tri'p is bent to place it under normal ten-y sion. l

26. In anA electromagnetic'translating device, a magnet system having an armature, a resilient Vibratory strip supporting said armature, and a pair of spaced supports for thelends of said strip, said supports having oppositelyinclined portions over which the strip is bent to place it under normal tension, said supports including adjustable screws to regulate thenormal position of said armature.

27. In an electromagnetic translating device, a laterally twistable spring .blade supported at its ends,an armature supported by said spring blade for vibratory movement, a magnet system operatively associated with said armature, and mean's for tilting the plane ot said spring blade'to adjust the normalposition of said armature, said means including kadjustable vscrews which act likeK positive stops to Acounter-act the pressure or thrust of the tensioned spring bladeA in a direction substantially at right angles to the screw-threads.

vice, a laterally twistablespring blade, supports for the ends of said spring blade, a

the normal position of the spring blade and armature, said adjusting means including adjustable screws which act like positive stops to counter-act the pressure or thrust of the tensionedspring blade in a direction substantially at right angles to the screwthreads.

28. In an electromagnetic translating de-v 29. In an electromagnetic translating device,.al magnet provided withpole'pieces arranged to form two airgaps, a` laterally twistable spring bladesupported atV its ends, an armatureconnected to the central portion of said spring blade and having' its ends in operative relation to said airgaps, and screws for 'adjusting said spring blade to regulate the normal posit-ionofsaid armature in said airgaps, said screws acting like positive stops to counter-act the pressure or thrust of the tensioned spring blade in a direction substantially at right angles to 'the screw,- i

threads. j l

30. In -an electromagnetic dev1ce,a permanent magnet, an armature `arranged for vibration betweenY the pole pieces vof. said.

magnet, and means to position said armature' to adjust the same and thereby cause said a mat'ure to rock into Vthe desired position, said screws acting like y positive stops to counterlact the thrust of the tensioned spring lade in ai` direction substantially at right angles to the 3l. In an electromagnetic deviceparvibrating armature, aliat spring connected at the center to saidV armature and having'bent end portions, supports orthe endM-portions` of said spring, and adjustable screw members which bear against the end portions of the spring to Hex themand hold themlirmly fixed in said supports. E y

A32. An electromagnetic translating device comprising. a permanent magnet structure having pole pieces with polar projections arranged to provide at least. l011e pair of aligned airgaps formed each betweenv two polar'faces of opposite polarity, said pole pieces and ,ail-gaps constituting parallel paths for the magnetic ux, the width ofcach `airgap being less than the'distance between polar projections` of the same polarity, an

parallel magnetic paths with aligned airgaps, said airgaps being formed between polar faces of opposite polarity and being narrower than the distance between polar projections of the same polarity an armature structure arranged to `vibrate between said airgaps in a direction substantially parallel with said polar faces and at right angles to flux across said airgaps acting in opposite directions `on the opposite'ends of said struc- `ture, the mounting of saidvibratory arma` ture structure being such that the gaps between the armature ends and adjacent pole faces remain substantially constant during the vibrationof said structure, while the overlapping areas between the armature ends and pole faces vary, and a pair of coils i n operative relation to said armature structure.v

ADoLPH A. THOMAS.

armature structure mounted to vvibrate, bel tween said airgaps, so that one end ofthe armature structure moves toward one of Said airgaps while the other end moves away from the other airgap in a direction substantially 4pz'nrallel with the polar faces of said pole pieces, and a pair of coils mounted on the Ymagnet pole pieces in operative relation to etic flux said armature structure, the magn being increased through one of said parallel Apaths and. simultaneously decreased through theother patlnl 33. An electromagnetic translating device compr a permanent magnet structure havinglslxiigumated pole pieces spaced to provide parallel magnetic paths with aligned airgaps, said airgaps being formed between polar faces of opposite polarity and `being narrower Ythan the distance between the bifurcations of each pole piece, an armature structure arranged'to vibrate between said airgaps in a direction substantially parallel with saidpolar faces and at right angles tc the passage of magnetic {iux across said airgaps, and a pair of coils mounted on said pole pieces m operative relation to said armature structure, the. relatioliof said polepieces and armature structure being such that the magl netic iiux is `increased through one of saidi paths and one end of said armature structure' andfis simultaneously decreased through the los gp other path and the .other end of said armaturestructure.

34. In an'eleetromagnetic translating de- 1ffice, an electromagnetic unit' comprising a permanent magnet vstructure having pole pieces with projections spaced to provide 

